I thought some other readers would have things to say about this but perhaps I shall respond to it for now quite a few days after you have posted the subject.
Blanching is quite needed for compressed teas unless you are going to boil it, like they do in Tibet.
A wash of hot water removes the very small leaf particles which release the content much more readily than the less broken leaves. These dusting/ fanning make controlling the infusion effect somewhat more difficult.
The step also opens up the leaf conglomerate so surfaces and parts of leaves that are otherwise buried inside can get in touch with the infusing water at roughly the same time as the exposed ones. Considering the exposed ones do have a slightly different chemistry because of exposure to the elements, a balance from the less exposed ones do help quite a lot.
I hope this helps
